1. Field of the Invention
The present invention relates to hem joints used in vehicular closure structures such as doors and lift gates.
2. Disclosure Information
Vehicle closure structures such as passenger doors, tailgates for station wagons and sport utility vehicles, and decklids and engine compartment hoods, commonly employ a construction detail wherein an outer panel is flanged over and joined with an inner panel. This flange joint, sometimes termed a “hem” joint, has been made up in a variety of ways, including by welding, adhesive bonding, and several types of mechanical joining. U.S. Pat. No. 5,237,734 illustrates a type of mechanical joining in which a raised rectangular bead is formed on one of the components to be joined, with the other component being stamped down over the bead, either with or without a slot being formed in the second component.
Known techniques for making up and joining hem flanges suffer from several deficiencies. In the case of structure shown in the '734 patent, the outer panel is not locked with the inner panel to the degree necessary to prevent torsional shifting of the outer and inner panels during handling of the panels prior to installation on the vehicle. And, welding techniques injure the outer surface of the panel, necessitating labor intensive and expensive metal finishing operations.
The present invention solves problems associated with known panel joining techniques by providing a 360° retention capability with a mechanical interlock, which combined with adhesive joining allows panels to not only be produced without torsional distortion caused by shifting of the inner and outer panels after the hem flanging operation, but which also avoids problems associated with corrosion and surface defects.